Orthodontists frequently find it necessary to apply protracting forces to a patient's teeth over prolonged periods of time. In some cases, the desired forces are preferably forwardly directed to urge the teeth outwardly away from the patient's mouth. The present invention provides a simple, stable device for applying such forces.
The prior art has evolved a variety of orthodontic protraction appliances. For example, U.S. Pat. No. 862,881 Case discloses a protraction appliance in the form of a headgear anchorage for applying corrective forces to the teeth. A retruding bow is held in front of the patient's mouth by elastic straps which form part of the headgear. The retruding bow can be connected to braces fixed to the patient's teeth to apply various forces to the teeth. Because the retruding bow is elastically supported at the back of the patient's head, Case's device is best suited to application of rearwardly directed forces and is generally incapable of applying significant forwardly directed forces in the manner of the present invention.
U.S. Pat. No. 2,334,894 Atkinson discloses an appliance having a frame which is strapped to a patient's head to position a spaced apart pair of parallel, vertical arms in front of the patient's face. A cross member extends horizontally between the arms. The ends of the cross member slidably engage the arms, allowing the cross member to be raised or lowered to position it at a desired level in front of the patient's mouth. Elastic bands, hooks, etc. can then be mounted between the cross member and braces applied to the patient's teeth, to apply the desired protracting force. Unlike the present invention, which provides secure bracing at the patient's forehead and sternum, Atkinson's device is braced between the patient's forehead and chin. Forehead-chin bracing is adequate to sustain application of corrective forces which are effective in some orthodontic correction procedures. However, forces imposed on the patient's lower jaw by an Atkinson type device can cause undesirable tempero mandibular joint displacement. This is preferably addressed by moving the maxillary posterior teeth forward, but such movement is not adequately achieved by the prior art.